This invention relates to a fuel supply adjusting system for an internal combustion engine and a method for use in the fuel supply adjusting system.
Internal combustion engines are widely used in driving vehicles, such as automobiles. An internal combustion engine is workable at a variable speed. Such a speed of the engine is called an engine speed in the art. An operator of the engine can work the engine at a commanded engine speed. This enables the vehicle to be driven by a driver at a desired speed in cooperation with a selected gear ratio.
A fuel supplying device is coupled to the engine. The fuel supplying device may have a controllable fuel injector orifice through which a fuel is injected into the engine. Furthermore, a speed adjusting device is coupled to the engine. The speed adjusting device may comprise a throttle valve which defines a controllable throttle value opening for an air flow to the engine. On accerelating the engine to the commanded engine speed, the operator controls the speed adjusting device to put the device into a varying state of, for example, increasing the air flow. A fuel supply adjusting system is coupled to the fuel supplying and the speed adjusting devices to adjust the fuel supplying device in response to the varying state.
A conventional fuel supply adjusting system is for detecting at first a previous and a current state which the variable state successively takes at a previous and a current instant of time, respectively. Responsive to the previous and the current states, the fuel supply adjusting system detects whether or not the engine is being accerelated. When the accerelation is detected, the fuel supply adjusting system calculates a rate of variation of the varying state in response to the previous and the current states. At the current instant, the fuel supply adjusting system makes the fuel supplying device supply an increased amount of fuel in response to the rate of variation.
The previous instant is a predetermined time interval prior to the current instant. The predetermined time interval should be short in order promptly to make the engine work at the commanded engine speed. Noise is, however, inevitably superposed on the calculated rate of variation. The predetermined time interval must therefor be relatively long. This results in a considerable delay in making the engine attain the commanded engine speed. Moreover, this prevents detailed detection of the accerelation and results in unsuitable operation of the fuel supply adjusting system. The results of the unsuitable operation are, for example, an unnecessary fuel consumption and insufficient operation of an exhaust emission control device which is attached to the engine for purification of exhaust gas.